Liquid Crystal Display Device, Method of Controlling the Same, and Mobile Terminal

1. A portable terminal having a liquid crystal display device, comprising: a display unit wherein pixels are arranged in a matrix on a transparent insulating substrate; and wherein some of the circuitry for a voltage-generating means is mounted together with the display unit on the transparent insulating substrate and the voltage generating means applying a common voltage to a common-electrode-side of all the pixels at a time other than power on/of time, and alternatively applying a voltage having the same level as that of a predetermined voltage, instead of the common voltage, to the common-electrode-side of all the pixels at power on/off time.

2. A portable terminal according to claim 1 , wherein a switching means selects an output voltage of the voltage-generating means at power on/off time.

3. A portable terminal according to claim 2 , wherein the output voltage of the voltage-generating means is a voltage applied to the common electrodes of liquid crystal cells in the pixels, or a voltage applied to electrodes of storage capacitors via CS lines.

4. A portable terminal according to claim 1 , wherein a switching means selects an output voltage of the voltage-generating means at power on/off time; and wherein the output voltage of the voltage-generating means is a voltage applied to the common electrodes of liquid crystal cells in the pixels, or a voltage applied to the common electrodes of storage capacitors of the pixels via a CS line.

5. A method of controlling a portable terminal having a liquid crystal display device, comprising both a display unit having pixels arranged in a matrix and voltage-generating means applying a common voltage to a common-electrode-side of all the pixels comprising: writing a predetermined voltage into each pixel of the display unit for a certain period of time while the voltage-generating means applies a voltage having a same level as that of the predetermined voltage to the common-electrode-side of all the pixels; wherein only some of the circuitry for the voltage-generating means is disposed on the same transparent insulating substrate as the pixel matrix of the display unit.

6. A method of controlling a portable terminal having a liquid crystal display device as in claim 5 further comprising: at a power off time, writing a predetermined voltage into each pixel of the display unit for a certain period of time while the voltage-generating means applies a voltage having the same level as that of the predetermined voltage to the common-electrode-side of all the pixels; and turning the power off.

7. A method of controlling a portable terminal having a liquid crystal display device comprising: a display unit having pixels arranged in a matrix and voltage-generating means applying a common voltage to the common-electrode-side of all the pixels and after the liquid crystal display device has been powered on, at a power off time, writing a predetermined voltage into each pixel of the display unit for a certain period of time while the voltage-generating means applies a voltage having the same level as that of the predetermined voltage to the common-electrode-side of all the pixels; and turning the power off; wherein only some of the circuitry for the voltage-generating means is disposed on a same transparent insulating substrate as the pixel matrix of the display unit.